Submitted to: Journal of Animal Science
Publication Type: Review article
Publication Acceptance Date: 9/30/1996
Publication Date: N/A
Citation: Interpretive Summary: Interpretive Summary not needed for this 115.
Technical Abstract: The neonatal pig is characterized by a high efficiency of nutrient utilization and rapid growth rate. The utilization of dietary protein for lean tissue growth is particularly efficient in the neonatal pig and is associated with a high rate of skeletal muscle protein synthesis and deposition. In support of these high growth rates, the neonatal pig consumes a milk diet that has a high biological value and is abundant in growth factors, including insulin and IGF-I. During the neonatal period, there are developmental changes in the circulating concentrations of, and tissue responsiveness to, hormones which play a central role in growth regulation, particularly insulin, IGF-I and growth hormone. Our goal has been to characterize the dietary factors and specific aspects of endocrine function that are responsible for the anabolic stimulus that helps to sustain the high rates of protein deposition in the neonatal pig. Our results suggest that, despite the abundance of growth factors in both milk and colostrum, the intake of nutrients is the primary anabolic stimulus for protein synthesis and this response declines with age. There is, however, a nonnutritive and as-yet-unidentified component in colostrum that provides a specific anabolic stimulus for skeletal muscle in the newborn, but this is probably neither insulin nor IGF-I. Our studies also indicate that increased circulating concentrations of IGF-I are only weakly associated with skeletal muscle protein synthesis, and that the primary endocrine signal that mediates the response to nutrient intake may be the tissue responsiveness to insulin. Future research should address how the local expression of IGFs affect the responsiveness of anabolic processes to nutrient intake and hence the efficiency of neonatal growth.